ANISOTROPIC LOW-FIELD MAGNETIZATION OF HEAVY-FERMION SUPERCONDUCTOR URU2SI2

Using a sensitive Hall-probe technique, the magnetization anisotropy o f the heavy-fermion superconductor URu2Si2, with T(c) = 1.2 K, was stu died as a function of magnetic field and temperature on a cube-shaped sample. The estimated first-critical-field values, H(c1), extrapolated to T = 0 are about 10 and 15 Oe for field parallel to the a- and c- c rystallographic directions, respectively. The low-field critical-curre nt density, J(c), exhibits a similar anisotropy as H(c1) but J(c) is s uppressed in particular by magnetic field oriented along the c-directi on. It is argued that results of magnetization measurements should dep end on the sample size and shape.